EFFECT OF POSTMORTEM TEMPERATURE ON CHICKEN M-PECTORALIS-MAJOR - ISOMETRIC TENSION AND PH PROFILES

1. The relationship between isometric tension development and pH, as a function of storage temperature between 0-degrees and 40-degrees-C, was examined in chicken M. pectoralis major (PM) muscle during the critical 24 h post-mortem period. 2. The muscle strips incubated at 0-degrees-C developed a peak isometric tension of 53-3 g/CM2 . This occurred after only 17 min incubation when the pH was 7.02, demonstrating the potential of chicken PM muscle to cold shorten. Peak isometric tension at 5-degrees-C was considerably lower than that generated at 0-degrees-C. However, as this occurred when the muscle pH was still high (6.70), this also indicated some potential to cold shorten at 5-degrees-C. 3. At 10-degrees to 30-degrees-C, the muscle strips developed mean peak isometric tensions of 18 g/CM2 after 6 h incubation by which time the muscle pH had fallen to 6.00, demonstrating a limited potential to rigor shorten. In contrast, those incubated at 40-degrees-C developed a peak tension of 54-5 g CM2 after 75 min when the muscle pH was also around 6.00, thus indicating the potential for intensive rigor shortening at this temperature. Incubation temperature and the resultant muscle pH therefore determine the potential of chicken PM muscle to either cold shorten or rigor shorten. 4. Despite the differences found in isometric tension profiles, cooked meat texture after isometric tension measurement was not significantly different at any of the temperatures studied primarily because the muscle strips were essentially prevented from shortening.